In a traditional archery bow, an archer must pull back with increasing force as he pulls the bowstring further back. Consequently, a great deal of strength may be needed to shoot an arrow with the full force of such a bow. This problem has been addressed with the advent of the compound bow, which employs at least one cam to create a draw force characteristic that actually decreases as the bowstring is pulled back past a certain point. The first compound bow had a cam at both the top and bottom of the bow to evenly leverage the draw force against the bow limbs. Unfortunately, with this arrangement it was difficult to keep the movement of the two cams synchronized as the bowstring was pulled back over repeated uses. To correct for this problem, a bow has been devised in which a single cam having a number of eccentric tracks is mounted at one end of the bow. Both ends of the bowstring cable are anchored to this cam and a grooved wheel is provided at the other end of the bow, around which the bowstring cable is looped. In this manner, there is no way for the bowstring cable feed out to be desynchronized as both ends of the cable are fed out by tracks that are rigidly fixed in place relative to one another on the single cam.
Unfortunately when an arrow is shot a compound bow, whether of the one cam or two-cam variety, loses a portion of the energy stored in the bow limbs to kinetic energy of the rotational members, which are accelerated rapidly to a swift rotation. This kinetic energy, in turn, causes the bow to ring at the end of the arrow shoot.
In a first separate aspect the present invention is a compound archery bow comprising a body having first and second flexible ends. A rotational assembly and a cam assembly are rotatably mounted on the body and spaced apart from each other. A bowstring has at least a portion of itself trained about the rotational assembly and is anchored to the cam assembly. In addition, an anchor cable has a first cable end fixed to the first end of the bow and a second cable end secured to the cam assembly. The cam assembly has a bowstring anchor projection and an anchor cable anchor projection for anchoring the bowstring and the anchor cable, respectively and an anchor cable track for taking in the anchor cable as the bow is being drawn. The cam assembly also has a bowstring track for letting out bowstring cable as the bow is being drawn and a mechanical linkage permitting limited relative motion between the bowstring cable track and the anchor cable track.
In a second separate aspect, the present invention is an archery bow cam assembly, including tracks for receiving cables, which may be placed into a first state wherein the tracks are in a first arrangement relative to one another or a second state wherein the tracks are in a second arrangement relative to one another. Mechanical energy is stored as the cam assembly is placed in the second state from the first state and is released as the cam assembly changes into the first state from the second state.
The foregoing and other objectives, features and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.